i02 7be Art of Farriery 



■rtb. The The V^vea is the fifth Coat, and makes the Cir- 

 ^^^'3. cumference of the Hole I have been defcribing, 

 which lies upon the Infide next the Cryjlalline Hu- 

 mour. This Coat is made of both circular and 

 ilraight Fibres or fmali Threads, which contraft or 

 dilate, according to the different Impreffions of 

 Light and Objefts : For, if the Light be flrong and 

 glaring, thefe Fibres contraft, and make the Hole 

 called the Pupil (or Sight of the Eye) appear fmaller. 

 In like Manner, thofe Colours which make a flrong 

 Impreflion upon the Retina^ oblige thefe Fibres to 

 contract and draw the Hole into a leffer Compafs ; 

 for the Contraftion is involuntary, as well as the 

 Dilatation or ftretching out of the Pupil. And by 

 thefe different Anions of the circular and ilraight 

 Fibres of the V'vea, one may very eafily judge of 

 the reft of the Parts of the Eye ; I mean, whether 

 they be found and perfeft. For, the more the 

 ftraight Fibres contraft, when the Animal is in Dark- 

 nefs, or has a dark or opaque Body held before the 

 Eye, by fo much the more may we judge the reft 

 of the Parts of this Organ to be in a found and 

 healthful State. The Contradion of the circular 

 Fibres is upon the Admiflion of the Rays of Light 

 into the Eye, and the quicker this Contradlion is 

 performed, the founder and more healthful are the 

 reft of the Coats and Humours. But, a Perfon who 

 is not well verfed in Opticks, muft look well, and 

 near, to obferve rightly the Contra6Upn and Dila- 

 tation I am fpeaking of. 

 No Con- Ii^ ^ Gutta Senna, the Pupil neither dilates nor 



tra<5tion or contra(fh j becaufe the Rays of Light which pafs^ 

 Dilatation this Hole, and fall upon the Retina,, do not in the 

 of the Pu- jg^^ ^^^^ fj^g Optick Nerve, which fhould convey 

 Gxitt" Se- the Image of the Objeft to the Brain. Therefore,, 

 rena, and in my Opinion, (notwithftanding what fome late 

 for what pretenders may fuggeft to the World, about their 

 Keafon. curing this Diforder of Sight) a Gutta Serena is in- 

 curable. And I dare venture to wager a Hundred 

 Found* with any Perfon, who pretends to perform 



this 



